What Causes a Toilet Tank to Crack?

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Take special care of your toilet's tank, especially if you have one made of porcelain.
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A toilet tank crack may be a sign that you need to install a new toilet or make a toilet repair. An unattended crack in a toilet tank just continues to grow until it starts to leak. These kinds of cracks may happen because of a number of factors, including age and accidents.


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Your toilet's tank operates by retaining water that you use during a flush and refilling it after you finish the flushing process on your toilet bowl. For that reason, it's important that it doesn't have a porcelain crack.


A toilet tank may develop a crack because of its age, careless handling or an accident.

Aging of Toilet Tank

Your toilet tank simply grows old after a period of time and starts developing some cracks in the porcelain. This is to be expected, as all bathroom fixtures do age. You might have an older tank made with a mixture of cement, causing the tank to get several cracks inside and outside it, especially if you have a major difference in temperature between the water inside the tank and the air outside.


If you have an old tank that has cracks branching out from one point because of age, you'd best buy a new one instead of trying to repair the older tank. Multiple cracks are likely to continue to spread. In such a case, it is highly unlikely you will be able to repair the cracks well enough that you won't experience leaks.

Toilet Tank Repairs or Adjustments

Any kind of repair performed on your toilet's tank might break a small piece of the tank because of the porcelain's delicacy. This kind of damage results from carelessness in handling the unit while making some kind of adjustment.


While tightening bolts around the tank, you might end up cracking it if you make the bolts too tight. While placing the lid back on the tank after doing an interior repair, take care not to set it down too hard or the porcelain cracks slightly at the top. These cracks may extend and later damage the entire tank.

Toilet Tank Accidents

Even small accidents, like dropping something light onto the tank lid, can cause the weight from the lid to push down onto the tank, causing pressure to build up and eventually cracking the top of the tank. If you fall from the shower, and use the tank to break your fall, the same is more than likely to happen as well, because of pressure.


Handle your toilet's tank with extreme and delicate care as you would with any type of porcelain. If the tank springs a leak, turn off the water supply to the tank immediately, and replace the toilet tank as soon as you can. You may still use the tank if you chipped off some of the top and the water doesn't leak, but you still must replace it as soon as possible.

Check Out Your Tank

To avoid an unexpected toilet tank leak, it helps to examine your toilet tank for cracks on a regular basis. At least once a month, carefully examine the tank for any signs of cracking. That way you can deal with the crack while it is still a minor problem. If you need to replace your tank or your one-piece toilet, Wayfair, Home Depot and similar establishments have options.



Mikhail Polenin

Mikhail Polenin has been working with computers since 1997. His experience also expands to astrophysics, masonry, electricity and general appliance repair. He's written about various different subjects regarding astrophysics and electrical circuits for various online publications. Polenin attended the New World School of the Arts and the University of Florida.